Raman studies of electronic excitations in Sr$_{2}$Ir$_{1-x}$Rh$_{x}$O$_{4}$

A novel Mott insulator Sr$_{2}$IrO$_{4}$ driven by strong spin-orbital interaction (SOI) has recently attracted a lot of attention. Small onsite Coulomb repulsion can open a gap in the SOC-induced J=1/2 states due to the narrow band. Interesting electronic phases in Sr$_{2}$Ir$_{1-x}$Rh$_{x}$O$_{4}$ were discovered by substituting Ir$^{4+}$ with Rh$^{4+}$, which can effectively tune the strength of spin-orbit interaction. We report results of a Raman scattering investigation of Sr$_{2}$Ir$_{1-x}$Rh$_{x}$O$_{4}$ from x=0 to x=0.7. The evolution of the phonon spectrum with Rh doping and temperature as well as the resonant profiles of phonons will be discussed. In addition, we also observed broad luminescence-like signal whose origin is not well understood. Latest results on high energy electronic excitations and luminescence will be presented.